If you are planning on selling tickets to your own personal “gun show” you better make sure the crowd will be impressed. The last thing you want is to throw up a biceps pose (with a big grin) and get “booed off the stage!” Unfortunately, while almost everyone in the gym tossing around the iron are quite passionate about filling out their shirt sleeves with muscle, most are making vital mistakes preventing this very goal from manifesting.
If you want a muscle to grow you must force it to do the work. Bending forward at the waist and swinging so that you can use more weight will only serve to take tension off your biceps, which in turn will hinder your quest for bigger guns.
Leaning back as you curl is not only a great way to injure the lower spine but also takes needed tension off the biceps. Tension is what makes a muscle grow, so stay upright throughout the range of motion until a perfect rep is no longer possible.
Some lifters think that they will get a better squeeze in the biceps if they raise up the elbows/shoulders at the top of a curl, but this simply is not true. All this will accomplish is to bring your anterior delts into the movement, which, once again, removes tension from the biceps and lessens the severity of their contraction.
In my 25 years as a coach/pro bodybuilder, one complaint I have heard quite often from trainees is that they get a better pump/burn in their forearms than in their biceps when performing all types of curls. For some, this is a case of having a strength imbalance between forearms and biceps that needs to be addressed/corrected. However, for most, this is an issue of technique. Make sure not to initiate curling exercises by first contracting the forearms – rather, keep the wrists in line with the forearms (or even bent slightly back) from stretch to contraction.
While there is nothing inherently wrong with training lats and biceps on the same day, if biceps growth is a priority then these two muscle groups are better done separately. Since back movements generally involve pulling, they tax the biceps and thus compromise the intensity you can put into your curls, which, will in turn hinder long-term gains in arm mass.
The eccentric (negative) contraction contributes greatly to anabolism (the processes that ignite hypertrophy) and should never be ignored when blasting the biceps! I can promise you that lowering the weight over 3-4 seconds on every rep (even if you have to go a bit lighter) will manifest into many more inches on your arms than curling and simply letting the BB or DBs drop back to the bottom.